The expressions “prime mover” and “work machine” are used within the context of this application with the following meanings: a work machine absorbs mechanical work in order to perform its task. A thermal fluid energy machine that is used as a work machine is thus operated as a compressor. By contrast, a prime mover performs work, wherein a thermal fluid energy machine for performing work converts the thermal energy that is available in the working gas. In this case, the thermal fluid energy is thus operated as a motor.
The expression “thermal fluid energy machine” is an umbrella term for machines that can extract thermal energy from a working fluid, in the context of this application a working gas, or supply thermal energy to said working fluid. Thermal energy is to be understood to mean both heat energy and also cold energy. Thermal fluid energy machines (also referred to for hereinafter for short as fluid energy machines) may for example be designed as piston-type machines. It is preferably also possible for use to be made of hydrodynamic thermal fluid energy machines whose rotors permit a continuous flow of the working gas. Use is preferably made of axially acting turbines and compressors.
The principle specified above is described for example in US 2010/0257862 A1. In said document, piston-type machines are used to perform the described method. Moreover, it is known from U.S. Pat. No. 5,436,508 that, by the installations specified above for storing thermal energy, overcapacities in the case of the utilization of wind energy for producing electrical current can be temporarily stored in order to be drawn upon again if required.